The field of the invention relates to engine control systems, including air/fuel and ignition control systems.
It is known no retard ignition timing to more rapidly heat engine exhaust gases and the catalytic converter coupled to the exhaust gases. Such a system is shown in U.S. Pat. No. 5,211,011 which also describes alternately running fuel delivered to the engine rich and then lean while the converter is below a desired temperature.
The inventors herein have recognized numerous problems with the above approaches. For example, an open loop lean fuel command which is intended to result in air/fuel operation slightly lean of stoichiometry may result in air/fuel operation leaner than desired causing rough engine operation and increased emissions. Such leaner than desired operation may occur as the engine and its components age (e.g., slightly clogged fuel injectors). Another problem is that lean operation may reduce engine power which is annoying to the vehicular operator when power is demanded.